A technology in the related art whereby a white pattern is photographed at each aperture value and correction information is recorded in advance to be used to correct the adverse effect of dust that has entered the optical systems while manufacturing a video camera is disclosed in Japanese Laid Open Patent Publication No. H9-51459. In addition, Japanese Laid Open Patent Publication No. H10-294870 and Japanese Laid Open Patent Publication No. H11-27475 each disclose a technology for detecting dust by taking in white reference data from a uniform reflecting surface prior to the original copy read, to be adopted in copiers in which the dust conditions may change constantly. Also, U.S. Pat. No. 6,195,161 discloses a method for obtaining an attenuation signal indicating the attenuation of transmittance attributable to a film defect by obtaining transmittance data concurrently as visible light data are obtained with an infrared sensor instead of the white reference data, to be adopted in scanners.